What should I be aware of when buying a zoom lens (other than that it will fit my camera)? What specs should I pay close attention to?
One consideration (this is a generalization, but most generalizations are based on some facts) is that usually the longer the zoom range, the quality of the image will suffer. As an example, the mega-zooms (28-300mm for example) will usually result in softer images (especially at either end of the zoom range) than a lens with a narrower zoom range (such as 24-70mm).
In any case, look for real-world reviews and photo samples before making a purchase.
I really like the lens review section of FredMiranda.com for getting real-world reviews.
- The zoom factor of course
- Aperture, if aperture value is low you will either be able to take better photo in darkness and/or do blur effect in lower focus distance
- Min. focus distance, you will not be able to take a correct shoot if subject is closer than this distance
- Weight depending of your need you might not want something too heavy
Each time you want to buy a lens, try to find some review on Internet !
If you know someone with the lens you are interested in, or a similar one, borrow and use it if you can. That goes way beyond reviews!
I'm a big fan of Thom Hogan's lens reviews. http://bythom.com/nikon.htm